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1、太原理工大学 博士学位论文 正交频分复用系统中降低峰均功率比算法的研究 姓名：李剑平 申请学位级别：博士 专业： 指导教师：王华奎 太原理工大学博士研究生学位论文 I 正交频分复用系统中降低峰均功率比算法的研究 摘 要 正交频分复用(Orthogonal Frequency Division Multiplexing ,OFDM)以其 有效对抗多径衰落的特性以及较高的频谱利用率而受到广泛关注，有望被 下一代（4G）移动通信系统所采用。但是 OFDM 技术却存在着一个不可避 免的缺点，即存在较高的峰均功率比( Peak to Average Power Ratio，PAPR) ， 这个缺点会导致
2、发送端对高功率放大器的线性度要求很高，且发送效率极 低，接收端对前置放大器的线性度要求也很高，并且还会增加模数/ 数模转 换器的复杂度。因此高的 PAPR 限制了 OFDM 在实际通信环境中的应用和 推广。本文就如何有效地降低信号的峰均功率比问题进行了研究，本文的 主要工作有以下几个方面： 1. 论文详细分析了基于离散傅立叶变换的OFDM 的发展进程、 系统原 理、关键技术及其主要优缺点。 2. 分析了 OFDM 信号出现高峰值的原因，对降低 OFDM 系统信号峰 均比的多种算法进行了研究和分析。对当前常用的三类降低 OFDM 系统中 PAPR的方法：信号预畸变技术、信号编码技术和信号扰码技术
3、的优缺点进 行了深入的研究和比较。 3.本文重点研究并仿真了信号扰码技术和信号预畸变技术及二者的结 合技术算法。 4.本文从不同的角度， 深入研究了多种可以有效降低峰均功率比的低复 杂度改进算法。其中包括：(1)利用交织分割法在分割顺序上的不同特点来 降低计算的复杂度。(2)从辅助加权信息的角度，提出了迭代 PTS 法，大大 降低了系统的复杂性。(3)综合 PAPR 性能和系统复杂度两方面，提出了双 层 PTS 法，该方法对 PTS 中辅助加权信息的优化提出了结构性的创新。(4) 太原理工大学博士研究生学位论文 I I 对上述算法均进行了系统的仿真研究和分析。仿真结果表明，改进算法与 传统的研
4、究算法相比，能够有效降低系统的复杂度，实现起来更加容易， 而它所带来的 PAPR 牺牲非常小。 5. 在研究分析限幅法和 PTS 法的基础上，进一步研究一种将部分传输 序列法与限幅滤波法相结合的新算法。通过仿真表明，该算法在不影响系 统性能的基础上，比单一的部分传输序列算法或限幅算法能进一步降低系 统的峰均比，而且系统复杂度没有受到影响。 6 研究分析了适合子载波数较大情况的T R 算法， 在 T R 算法的基础上， 为了进一步提高算法在不同子载波数情况下的性能，本文引进了混沌变量 迭代法，提出了基于混沌变量的改进型音频保留算法，对小子载波的降峰 核和大子载波的迭代算法进行了改进。 最后，对本
5、文所做的工作做出认真的总结，分析了工作中取得的成绩 和需要改进之处，并展望了今后的研究方向。 关键词：正交频分复用，峰均功率比，部分传输序列，音频保留法，混沌 变量迭代法 太原理工大学博士研究生学位论文 I I I THE RESEARCH ON REDUCING PEAK- TO- AVERAGE POWER RATIO IN OFDM SYSTEM ABSTRACT Orthogonal Frequency Division Multiplexing（OFDM) is expected to used in the next generation mobile communication
6、system(4G) for the extensive attention on effective against multi- path fading characteristics and more spectrum efficiency. This technology, However, still has an unavoidable drawback on high Peak to Average Power Ratio(PAPR), which lead to higher requirement for High Power Amplifier at transmitter
7、 and receiver, lower transmission efficiency, and also more complexity for (A/D) and (D/A) transmission modes. The disadvantage of PAPR limits the application and popularity of OFDM in actual communication environment. In this paper, the study focuses on how to effectively reduce the PAPR in OFDM sy
8、stems, which including followings aspects: 1. The principle of DFT- based OFDM system, key techniques, advantages and disadvantages of OFDM technology are analyzed in this paper. 2. Analyze the reasons as higher PAPR happened, study the more algorithms to reduced PAPR in OFDM. For the most popular t
9、hree kinds of PAPR reducing techniques, which are pre- distorting technology, coding technology and scrambling technology, also make more analysis and compare. 3. This paper focuses on the algorithm for signal scrambling technology, signal pre- distortion technology and their combination technology.
10、 4. In this paper, from different aspects to study variety low complexity improved algorithm to effectively reduce the peak to average power ratio. These methods including: (1) To consider the particular characteristic and adopt interleaved partition method to reduce the PTS s complexity. (2) Iterat
11、ive PTS is proposed from the way of assistant weighed index, which reduced computation 太原理工大学博士研究生学位论文 I V complexity by a long way. (3)Beside on the PAPR performance and system complexity, double PTS is proposed, which has a structural innovation to optimize assistant weighed index. (4) Make more s
12、imulation and analysis to above algorithm. The results of simulation show that these schemes, which are less complex and more easily implemented, suffer little PAPR performance degradation. 5. Based on the research on Clipping method and PTS method, taking two algorithms combined, one is Clipping an
13、d Filter and the other is Partial Transform Sequence. The simulation results show that the algorithm has been reduced PAPR than the algorithms of single Clipping Filter and Partial Transform Sequence, the complexity of system also has not been affected. 6. Study the Tone Reservation (TR) algorithms
14、which suitable for the large carrier number system. Based on TR, i n order to increase performance of the Tone Reservation method in different carrier number, chaotic variable is introduced in the paper, including PRT improvement under small carrier number system and improvement of SCR algorithm und
15、er large carrier number system. Through theoretical analysis as well as the simulation, the result indicated that the performance of CCDF is better than the original algorithm in reduction for the PAPR of OFDM system signal. In the end of paper, summarize the study works, analyze the achievements an
16、d insufficiencies which need to be improved later, make an expectation of the further works. KEY WORDS: Orthogonal Frequency Division Multiplexing(OFDM), Peak to Average Power Ratio(PAPR), Partial Transmit Sequence(PTS), Tone Reservation (TR)，Iterative algorithm on chaotic variables 太原理工大学博士研究生学位论文 VIII 符号及缩略词说明 H：信道矩阵 N t ：码元周期 k f ：载波频率 f：子载波之间的频率间隔 g T： 保护间隔 w： 过采样因子 E ：表示求数学期望 ( )uR：自相关函数 p： 概率密度函数 CR： 限幅率 CF： 峰值参数 ( )C ?：压缩变换 ： 压扩率 ap R：冗余比特数 )(m i P：随机相位旋转因子 v b ： 辅助加权系数
